Operator manipulation of the automatic transmission of a motor vehicle is typically accomplished by way of a shift lever mounted either on or near the steering column of the vehicle or in or adjacent a console mounted on the floor of the vehicle between the driver's seat and the front passenger seat. The shift lever is mounted for primary movement between a PARK position and the Forward and Reverse driving positions, usually separated by a "Neutral" position. The shift lever is also mounted to provide a release movement, usually at right angles to the primary movement, through which a pawl is lifted out of and seated into a detent to hold the shift lever in the PARK position and prevent inadvertent movement of the lever in the primary mode; i.e., from PARK to one of the drive positions. The release movement can be implemented in several ways including (a) lateral shift lever movement, (b) fore-and-aft shift lever movement, (c) axial shift lever movement, and (d) depression of a push button.
Beginning in about the late 1980's automobiles manufactured for sale and/or use in the United States have been equipped with one of several types of shift lever interlocks, the most typical being a solenoid-implemented interlock which prevents the shift lever from being moved out of the PARK position until the operator has activated the ignition circuit and depressed the brake pedal. Depression of the brake pedal closes a switch normally associated with the brake light circuit to either supply or cut off the supply of power to a solenoid coil thereby to position an armature connected pin. Depending on the particular implementation of the interlock the solenoid pin can be used to latch either the shift lever primary movement or the release movement.
The interlock, although commonly involving the brake light circuit, can be associated with any automotive system capable of producing an appropriate electrical signal; e.g., a seat belt switch or a seat occupancy switch. Examples of such interlocks are illustrated in U.S. Pat Nos. 4,854,193 and 4,986,399.
U.S. Pat No. 4,887,702, assigned to United Technologies Automotive, Inc., discloses an interlock for a floor mounted shifter in which both a mechanical ignition lock and a brake/shift lock solenoid are connected to a pivotally movable PARK/LOCK member in the shifter by means of one or more cables. According to the further disclosure of U.S. Pat. No. 5,027,929, also assigned to United Technologies Automotive, the cable implemented interlock of U.S. Pat No. 4,887,702 requires not only one or two relatively expensive cables but also requires a relatively precise cable length adjustment procedure during installation to ensure that the solenoid will operate properly.